You see that there is the difference, a marginal mistake doesn't compare to a massive one, one is a slight miscalculation, the other is evidence of a complete lack of understanding of how to play the position.
How come you didn't mention the backpass in your post?
Sorry to go on about Valencia, but I suppose I should address the post.
Has Valencia made loads of these offside positional mistakes? If so, I was´t aware of them. Feel free to post some specific examples, and not just the typical baseless generalizations. Wouldn´t you suppose he has a very good understanding of how to play the position, considering he is still here, playing for one of the elite clubs in the world, and Rafa was flogged off, and LVG has brought him in more than once when Darmian was too shite to continue, and he responded adequately. Seems like he probably understands very well, has the gaffer´s confidence, and likely still learning a thing or two being that he´s fairly new at fullback.
And yes, if it makes you feel better, the backpass was a horrible mistake. Valencia, like everyone else, is prone to a few.